Minnesota Crash

[EricJ]

2 hours ago, jlunseth said:

Aside from issues with the data, the rounding effect or whatever you want to call it, will distort climb and descent rates over altitude changes of a few hundred feet, which is what we are talking about with this incident. Here is a simple example. The transponder reports in increments of 100 feet so it necessarily rounds up or down at some point. Let’s say it does that at 50 feet. So if you are flying at 3040 the transponder reports 3000 (setting aside the pressure altitude issue for the moment). At 3060 feet it reports 3100, so it says you have ascended 100 feet between the two ADSB broadcast although the actual altitude change was just 20 feet. The maximum distortion is about 200 feet of altitude. Say you start at 3040 and ascend to 3160. You would ascend 120 feet but ADSB would report 300. 

My simple example is just to explain the rounding effect, but it is more prevalent in real life flying and not as clean as in my example. I flew with an MX20 for many years that reported encoder altitude, altered for local pressure. It was always off and in weird amounts. If you are climbing or descending, say, 10,000 feet the potential distortion is still only 200 feet so percentage-wise it is small. But if you are going from 3000 to 3100 the distortion can be substantial.

I did a tour of an ATC facility years ago. They told us they are aware of these issues and do not pay attention to reported altitude changes of less than 200 feet.

As I said in my earlier post there is no doubt there was a significant altitude and speed change in this instance. I am just saying we can’t use that data at the granular level we would like because it is just not that accurate. Also, I would like to see the actual data and know how it was put together. I read the ADSB Exchange web page, it looks like the data is harvested by hobbyists with a Raspberry Pi, a Software Defined Radio and an antenna. I looked at sample data and it is not in the format that it is presented in the graphics in this thread, so at some point the actual data is translated. How, what choices are made? Are parts of the data from multiple harvesters put together into one data stream? Is it AGL, MSL, pressure compensated (it appears not to be)? I am not saying it is not useful, I would certainly not stake my life and fly my aircraft based on the data, not at this point. Notwithstanding, it is still interesting and it is data.

It's not really rounding error.   ADS-B-out data includes both pressure and geometric (gps) altitude, and the geometric altitude has enough precision that rounding errors are not very significant.   With a WAAS corrected source, the geometric altitude should be reasonably accurate as well.   (Since there's the usual difference between precision and accuracy.)

That said, the ADS-B data used for the calculations probably doesn't indicate which was used, pressure or geometric, or how much or what processing (averaging, filtering) was done on the data.    Undoubtedly, however, the FAA and NTSB know the differences in the ADS-B data and can utilize it and come to more supportable conclusions than could be done without knowing the details.

Geometric (gps) position data, including altitude, from a WAAS GPS source should be pretty accurate and provide reliable data.   This is what is used on LPV approaches, so if you don't have confidence in it, you should not use it for GPS with a glidepath or vertical guidance.

 

[chriscalandro]

That wing loading is going to become as overplayed in performance discussions as Al Mooney’s height in new buyer discussion isn’t it. 
 

in both cases it’s a number that doesn’t really mean anything when you factor in all the variables. 
 

there is a huge difference between static force and dynamic force. 

Edited August 16, 2021 by chriscalandro

[GeeBee]

I swore I would not say anything, but......... 17 pages of speculation, debate on very sketchy data and video and no access to the wreckage. I'm prepared to wait for the report rather than speculate on something without really solid data. Nobody is in danger of falling out of the air here.

[A64Pilot]

On 8/16/2021 at 11:37 AM, chriscalandro said:

That wing loading is going to become as overplayed in performance discussions as Al Mooney’s height in new buyer discussion isn’t it. 
 

in both cases it’s a number that doesn’t really mean anything when you factor in all the variables. 
 

there is a huge difference between static force and dynamic force. 

Yes, but dynamic is hard to test to, so we test static, but even static it’s only required to hold for 3 sec. 

Static load testing has served us well for a Century, it’s fatigue thats difficult to design for, to begin with you have to have an accepted flight profile.

The FAA has been preaching for years that older GA aircraft will start falling out of the sky, they try to say the T-34 is the Canary in the Coal mine.

My personal belief is that corrosion is a larger factor for the average older airplane.

[Shadrach]

On 8/16/2021 at 11:37 AM, chriscalandro said:

That wing loading is going to become as overplayed in performance discussions as Al Mooney’s height in new buyer discussion isn’t it. 
 

in both cases it’s a number that doesn’t really mean anything when you factor in all the variables. 
 

there is a huge difference between static force and dynamic force. 

“It doesn’t mean anything” ???

Sometimes a bit of hyperbole works when trying to prove a point and sometimes it makes the person employing it appear obtuse. It’s not difficult to acknowledge that dynamic and static forces are different. It’s a bridge too far to suggest that a wing that broke the test rig at 9.5Gs under static testing “doesn’t mean anything“.  My initial response was to another poster that suggested the wing would fail at 6.7Gs. The fact that the wing with stood a static load more than 40% higher then 6.7Gs certainly means something. Saying that it does not is patently STUPID. 
Furthermore, the airframe is known to have survived dynamic loads well exceeding the aforementioned 6.7Gs. The factory estimated that the aircraft in the accident linked below experienced in excess of 12Gs in-flight during recovery from an upset that occurred 10,000ft above the recovery altitude.

There’s definitely a number. A handful of ham fisted pilots have found it…however, 6.7Gs ain’t it.

[chriscalandro]

1 hour ago, Shadrach said:

“It doesn’t mean anything” ???

Sometimes a bit of hyperbole works when trying to prove a point and sometimes it makes the person employing it appear obtuse. It’s not difficult to acknowledge that dynamic and static forces are different. It’s a bridge too far to suggest that a wing that broke the test rig at 9.5Gs under static testing “doesn’t mean anything“.  My initial response was to another poster that suggested the wing would fail at 6.7Gs. The fact that the wing with stood a static load more than 40% higher then 6.7Gs certainly means something. Saying that it does not is patently STUPID. 
Furthermore, the airframe is known to have survived dynamic loads well exceeding the aforementioned 6.7Gs. The factory estimated that the aircraft in the accident linked below experienced in excess of 12Gs in-flight during recovery from an upset that occurred 10,000ft above the recovery altitude.

There’s definitely a number. A handful of ham fisted pilots have found it…however, 6.7Gs ain’t it.

There is very little correlation with a dynamic load and a static load.  An airplane deals with dynamic loads and encounters fatigue in the short term and in the the long term.

 

The static load of a wing 30 years ago means nothing to a wing that encounters a dynamic loads today.  Once the wing has left the building and received any amount of use the static load required for it to break will change.

 

It doesn't mean anything.

Edited August 17, 2021 by chriscalandro

[Schllc]

The laws of physics and properties of known elements, seem to have left the conversation....

[Mooney in Oz]

5 hours ago, Shadrach said:

 

From FL160 to 6,000 feet in severe turbulence. That's a drop of 10,000 feet resulting in 12 g's of force with the aircraft staying together and the pilot, thankfully surviving the ordeal. 

It just blows my mind how this latest accident happened and the horrific end result when the above circumstances was nothing like what recently happened.

[chriscalandro]

31 minutes ago, Schllc said:

The laws of physics and properties of known element seem to have left the conversation....

You are talking about a discussion that started with pages of people arguing that the wing became disconnected and completely vertical within a single frame of video.

[A64Pilot]

At some point you lose consciousness, I’d assume 12G’s may be past that point?

[Hank]

1 hour ago, A64Pilot said:

At some point you lose consciousness, I’d assume 12G’s may be past that point?

It is for most people. Usually. 

[David Lloyd]

Recently did a little reading on G forces.  Wish I could find the article for a link.  Most people, anything over 4 Gs for more than 3 or 4 seconds will put them to sleep.  With recent experience, practice, and use of breathing and straining techniques, you might take a little more G or a little more time.

About 3.5 Gs was my limit for fun.  More hurt.  I learned to be careful with anything more.  Once with a passenger that wanted to see a tight turn, I banked and pulled about 5 for a few seconds before easing off.  Looked over and he had his head on his chest.  A few seconds.

12?  Your head would probably slam the yoke, then your knee.

[aviatoreb]

11 minutes ago, David Lloyd said:

Recently did a little reading on G forces.  Wish I could find the article for a link.  Most people, anything over 4 Gs for more than 3 or 4 seconds will put them to sleep.  With recent experience, practice, and use of breathing and straining techniques, you might take a little more G or a little more time.

About 3.5 Gs was my limit for fun.  More hurt.  I learned to be careful with anything more.  Once with a passenger that wanted to see a tight turn, I banked and pulled about 5 for a few seconds before easing off.  Looked over and he had his head on his chest.  A few seconds.

12?  Your head would probably slam the yoke, then your knee.

From memory - which may be faulty - did the Apollo astronauts need to pull 9 g's during lift off?

How many g's to fighter pilots pull in their most extreme maneuvers (for anyone here?  Jobe?).  How many g's can the fighter jet airplanes pull vs how many can the soft squishy bio-materials pilots pull?

[tmo]

39 minutes ago, aviatoreb said:

How many g's to fighter pilots pull in their most extreme maneuvers

To be fair, they do have the special suits that inflate wherever and however much they need to.

[aviatoreb]

4 minutes ago, tmo said:

To be fair, they do have the special suits that inflate wherever and however much they need to.

true - true.

 

[Hank]

11 minutes ago, tmo said:

To be fair, they do have the special suits that inflate wherever and however much they need to.

Yes, those help, but there are still limits that vary, pilot to pilot. 

[Will.iam]

IIRC you had to make it to 9 g’s in the centrifuge to get f-15 f-16. 7 g’s for A-10 there was a time limit too but can’t recall. Anything over 4 g’s just sucked and I couldn’t tell the difference between 4 up to the limit of the T-37 at 6.7 if it wasn’t for looking at the G meter. 

[Will.iam]

Also an interesting fact by the time your body triggers that you are thirsty, your g tolerance was at 50%. Hydration was huge but I also subconsciously think the fear of pissing yourself if you passed out now because you had a full bladder from all the water you just drank before the sortie was extra motivation to stay awake. 

[AH-1 Cobra Pilot]

1 hour ago, aviatoreb said:

From memory - which may be faulty - did the Apollo astronauts need to pull 9 g's during lift off?

How many g's to fighter pilots pull in their most extreme maneuvers (for anyone here?  Jobe?).  How many g's can the fighter jet airplanes pull vs how many can the soft squishy bio-materials pilots pull?

It depends on a few things.  F-16s have seats that are tilted back, so they can take a little more than a more upright seat.  Some other aircraft may also have that.  The pilot's body shape and composition are important.  Shorter can take more Gs than taller; more muscular build can take more; amount and recency of G-experience is also favorable.  It also makes a BIG difference how long you hold the Gs.

Being ready for the Gs is critical, so you can prepare.  The GIB may be looking over his shoulder when the GIF pulls an unexpected maneuver, so the GIB passes out.  Tightening your muscles prevents blood from flowing as easily, so you will be able to withstand more Gs.

G-suits only add about 1/2G to what you can take.

I have been through 6Gs, and it can be painful.  I have passed out from Gs, and also temporarily lost my vision due to Gray Out, (or Brown Out).  At an airshow, my boss, (F-14 RIO), took a ride with Joann Osterud in her Hiperbipe.  At the time, she owned the world record for 206 consecutive outside loops.  He said that after three, he was in such pain he had to get back on the ground.

Edited August 18, 2021 by AH-1 Cobra Pilot

[David Lloyd]

2 hours ago, aviatoreb said:

From memory - which may be faulty - did the Apollo astronauts need to pull 9 g's during lift off?

How many g's to fighter pilots pull in their most extreme maneuvers (for anyone here?  Jobe?).  How many g's can the fighter jet airplanes pull vs how many can the soft squishy bio-materials pilots pull?

I saw a video either here or Beechtalk, a couple weeks back about the Saturn V and it was 1.25 at launch, building to almost 4 at T+135. At that point the center engine was shut down.  Maybe the third stage right before running out of gas peaked around 5.  Remember, those guys were laying on their backs, not sitting up.  Re-entry may have been more.  Gotta go read more trivia now.

The high G for fighter pilots, is a matter of preparation, training, experience and recent experience.  The G suit helps a little.  Over 4 is hard work.  Us soft squishy guys, it hurts.  Tolerance on any particular day depends on physical condition, hydration, time of day, a hundred other things.  Uh, what AH-1 Cobra Pilot just said.

 

[jlunseth]

Here is some footage I found from a local TV station of the left stabilizer and elevator. It is not clear in this footage, but there is other footage showing that the elevator is torn in half about in the middle. The NTSB commented that “portions” of the left stabilizer and elevator tore off, but I think he must have meant portions of the entire stabilizer/elevator because it is clear from the footage that there was very little if any of either the left stabilizer or the left elevator still attached to the aircraft. The whole of both of them appear to be in the neighbors yard, two blocks from the crash. The footage also describes that the wings are folded and the aircraft is tumbling or spinning, not flying. The stabilizer footage starts at 2:15 and the elevator after that. https://www.fox9.com/news/neighbors-ran-to-help-after-plane-crash-in-victoria-minn

My speculation, but it appears that the stabilizer sustained some kind of folding at the root, from the look of the sheet metal. Also my speculation that the outside half of the elevator tore off, then the inside half. 

[LANCECASPER]

Heartbreaking to read all of this. 

Sounds like a domino effect  . . possibly defective attitude indicator or maybe medical emergency*, then loss of control, maybe spatial disorientation, then stall spin. If the airplane is way past Vne and you pull back hard on the yoke, I can see the elevator being torn off. What a huge loss for the family and the communities in which they lived.

(*If it was a medical emergency it must have been a helpless few minutes for the daughter on-board who was a medical doctor and her husband who was an EMT. For people that regularly fly with us, the Pinch Hitter courses would be invaluable in at least being able to communicate and possibly get the airplane back on the ground.)

[bradp]

From the news report footage 

Looks like original steam gauges from what I can tell

 

[EricJ]

I've been wondering whether this was exacerbated by previous stress that led to a failure under less than expected load.   Previous damage or improper repairs or unreported events exceeding Vne might be contibutors and it might be difficult to tell.

Since many of our airplanes have long histories and lots of flight hours, there's no telling how much they've been previously stressed.   Not all potentially affected areas are easily inspectable.    My airplane was a rental for a period of its life, so there's no telling what previous extreme stresses it has experienced from renters or from flights through weather or whatever.   

[Ragsf15e]

On 8/18/2021 at 1:35 PM, aviatoreb said:

From memory - which may be faulty - did the Apollo astronauts need to pull 9 g's during lift off?

How many g's to fighter pilots pull in their most extreme maneuvers (for anyone here?  Jobe?).  How many g's can the fighter jet airplanes pull vs how many can the soft squishy bio-materials pilots pull?

I can comment on this… F-15 profile goes to 9 gs just like the F-16.  F-22 and -35s have a different/better g suit setup.  The f-16s do have a slight difference in seat incline.  The actual airplane can sustain 9gs in flight (F-16) or something more like 8 (F-15).  A normal, athletic person can’t do that without a g suit and training and currency.  Someone who knows how to strain and has very strong legs/abs might tolerate 8 gs for say 15”, but it is very hard work.  A random 70 year old, not so much.

At ~22 years old and reasonably fit, I did the F-15E profile.  Part of it is a resting g tolerance.  No strain, no suit.  When the world starts to grey out you’ll can start to strain.  I was about 3.5 gs.  I passed the centrifuge course at 9gs that day.  Straining properly is the most effective and the g suit adds about 1, but it also helps you strain.  It is exhausting for any length of time.  Until you’re really use to it, you’re exhausted after a BFM sortie fighting another jet.

The centrifuge is one of the worst experiences ever.  You’ve never been so exhausted, dizzy or sick in your life.